Lamp base with collared insulator



June 6, 1961 H. L. RUDLER EI'AL 2,987,696

LAMP BASE WITH COLLARED INSULATOR Filed 001'. 24, 1957 Invent'ovs: Henry L. RuclLeT",

Havotd (-1. Nelson,

b9 Their A L- orheg- United States Patent() 2,987,696 LAMP BASE WITH COLLARED INSULATOR Henry L. Rudler and Howard G. Nelson, Conneaut, Ohio, assignors to General Electric Company, a corporation of New York Filed Oct. 24, 1957, Ser. No. 692,214 4 Claims. (Cl. 339-146) The present invention relates to electric lamp bases of the type comprising a metal shell, a center contact and a molded insulator uniting the shell and the center contact at one end of the base.

Bases of this type have been used commercially for more than fifty years for incandescent lamps of various sizes and wattages. Screw threaded Shells as well as smooth-walled shells provided with outwardly projecting pins for engaging electrical sockets for such lamps are used extensively at present. The molded insulator not only unites the shell and the center contact but also defines a funnel-shaped passage leading from the interior of the shell into an opening in the center contact to facilitate threading of an inlead wire through the base for attachment to the center contact during assembly of the lamp bulb and the base in the manufacture of a based lamp. Molded glass insulators are used extensively, but molded insulators of thermo-setting organic plastics are also used.

Heretofore, in commercial bases, the base shell has been provided at one end with a flange the rim portion of which has been wholly embedded in the body of the glass or the organic plastic insulator to hold the shell and the insulator against relative movements. The insulator filled the entire cross-section of the flanged end of the shell.

It has been proposed to provide the shell with a reentrant bezel at one end of the shell in the form of a curved-sided flange no part of which is embedded in the insulator and which partially surrounds the insulator to hold it in the base shell. In the proposed structure, the flange on the shell extends inwardly of the shell as far as the insulator and terminates in an exposed edge partially overlapping the inner end of the insulator. The provision of a curved-sided flange complicates the manufacture of the base shell and the exposed edge thereof reduces the safety factor of the base by increasing the ossibility of the inlead wire fastened to the center contact engaging the edge portion of the flange after the wire has been attached to the center contact in the manufacture of the lamp. Such engagements between the inlead wire and the edge portion of the flange would of course result in short circuiting the filament of the lamp to terminate the useful life of the lamp, among other disadvantages.

Bases of the proposed type have not been sold in this country up to the present time as far as applicants are aware, probably because of the complexities in forming the curved-sided re-entrant flange on the shell on -a mass production basis and the lower safety factor of such bases as compared with present commercial bases.

Bases of the proposed structure offer advantages not present in present commercial bases in that the quantity of glass or organic plastic material necessary for forming the insulator within the flange is substantially less than in present commercial bases wherein the insulator fills the entire cross section of one end of the shell. Reducing the quantity of the insulator material is highly advantageous in that it reduces the cost of the organic plastic type of insulators as well as that of glass insulators. A particular and further advantage of reducing the quantity of glass needed to form the insulator is in the reduction in heat imparted to the metal from the moltenglass during manufacture of the lamp base. By reducing the quantity of glass the quantity of heat is correspondingly reduced to the end that the number of shells rejected because of weakness resulting from overheating of the metal shell during introduction of the molten glass and molding of the glass insulator in the shell can be reduced to lower the cost of manufacturing such bases on a mass production basis. This also makes possible a reduction in the thickness of the shell Wall without reducing the strength of the base below acceptable limits, thus effecting a considerable saving in metal for the base shell.

In spite of the possibilities of making large savings in material offered by the proposed base, no such bases are available commercially at present as far as applicants are aware. V v g The principal object of the present invention is to overcome the defects pointed out above in bases of the proposed type and thereby provide such bases of commercially acceptable structure for the first time. Further objects and advantages of the invention will appear from the accompanying drawing showing species thereof, the following detailed description and the appended claims.

A feature of bases embodying the invention is a metal shell having at one end a straight-sided re-entrant flange which engages and extends around the insulator and an insulator which extends inward of the shell beyond the edge of the flange and completely covers the edge. The edge of the flange is insulated in a positive manner by this structure so that short circuiting engagements between the flange and the inlead wire connected to the center contact in the based lamp cannot occur.

The insulator also extends outward beyond the flanged end of the shell and overlaps the shell at this end. The flange thus serves as a collar on the insulator to prevent relative movement of the shell and the insulator. Base shells provided with re-entrant, straight-sided flanges of this kind are readily manufactured on a mass production basis on existing automatic base shell making machines with but slight modification of the machines and at minimum cost. The insulator is readily formed in the shell with slight modifications of existing automatic base making machines.

In the drawing accompanying and forming part of this specification, two species of lamp bases embodying the invention are shown in which;

FIG. 1 is a sectional elevation of a screw-thread type of base and showing in full lines the end of a lamp bulb of an incandescent lamp to which the base is attached;

FIG. 2 is a plan view of the base shown in FIG. 1 detached from the end of the lamp bulb, taken in the direction of the open end of the base shell and showing the interior of the base; I

FIG. 3 is an elevational fragmentary view of the base shown in FIGS. 1 and 2 with part of the base shell cut away to show the edge of the re-entrant flange and the insulator covering the edge;

FIG. 4 is a sectional elevation of a bayonet type of base having extruded pins on the base shell;

FIG. 5 is a plan view of the base shown in FIG. 4 taken in the direction of the open end of the base shell and showing the interior of the base, and

FIG. 6 is a fragmentary sectional elevational view of a mold and die plunger arrangement suitable for molding the insulator of the base shown in FIGS. 1 to 3.

Referring to FIGS. 1, 2 and 3 of the drawing, the lamp base 1 comprises a tubular, thin-walled metal shell 2 provided with external screw threads '3 to enable the screwing of the base into a screw-threaded type of lamp socket. The base 1 is shown attached at its open end to the neck 4 of the glass bulb 5 of an incandescent lamp by the conventional. basing cement 6. The opposite end of the shell 2 is domed, as shown at 7, and provided with a re-entrant flange 8 of frusto-conical shape tapering toward the domed end 7 and extending inwardly of the shell to about the level at which the threaded portion of the shell begins, as best shown in FIG. 1.

A molded glass body or insulator 9 extends through the opening defined by the re-entrant flange 8 and supports a center contact or eyelet 10 of brass having an aperture 11 through which the inlead wire 12 extending from the neck of the bulb is threaded during assembly of the base on the bulb. In FIG. 1 of the drawing, the inlead wire 12 connected to one end of the tungsten filament (not shown) in bulb 5 is shown soldered to the end contact at 13. The solder 13 closes the aperture 11 in the contact and provides a rounded surface for engaging the center contact of the conventional screw-type of lamp socket in the usual manner.

The insulator 9 is molded by the means shown in FIG. 6 and describedbelow in the form and location shown in FIG. 1 while the glass is hot and plastic. The insulator defines a funnel-shaped passage 14 leading from the interior of the base 1 to the center opening 11 in the eyelet for facilitating the threading of the inlead wire 12 through the base in assembling the lamp bulb 5 and the base 1. The other inlead wire 15 connected to the opposite end of the filament in the bulb 5 is secured to the outside of the'shell at its end around the bulb 5, by a small drop 16 of solder, as shown inFIG. 1.

The insulator 9, as shown at 17 in FIGS. 1 and 3, extends inward of the shell 2 an appreciable distance beyond the edge 18 of the flange 8 and is molded so as to cover completely the said edge, as shown in FIGS. 1, 2 and 3. In the manufacture of the base shell 2 the flange 8 is ruptured or lacerated at its edge portion 18 by the'usual shell stamping operation resulting in a plurality of splits 19 (FIG. 3) providing a corresponding number of crevices spaced around the edge and extending longitudinally of the flange 8 from its edge'18. The glass, while plastic. is molded by the means shown in FIG. 6 in such manner that it flows into the crevices 19 while being molded in the form of the insulator 9 and, on solidifying, provides a positive lock with the flange 8 against relative rotation of the shell 2 and the insulator 9.

In addition to the positive locking feature provided by the above-described structure, the portion 17 of the glass insulator 9 extending beyond and covering the lacerated edge 18 of the flange '8 as shown in FIGS. 1 to 3 prevents the inlead wire 12 connected to the contact eyelet 10 from coming into contact with the edge 18 of the flange in the event the inlead wire is not pulled through the base a suflicient distance to straighten it in'mounting the base '1 on the bulb 5. Thus, the base structure shown in FIGS.

the completed lamp.

. The opposite end 20 of'the insulator extends outward beyond the domed end 7 of the base shell 2 and partially overlapsthe said end at the curved portion 21 connecting, the straight-sided flange 8 and the domed part 7. of the shell 2. Relative end-wise movement of the insulator 9. and the shell 2 is prevented in 'a positive manner by. the part 17 of the insulator overlapping and covering the edge 18 of the flange 8 and the part 20 thereof overlapping the curved part 21 between the dome 7 and the flange 8. By thisconstruction, insulator 9 has, in effect, a circumferential groove in its outer surface and between its ends. which accommodates and engages flange 8. The flanges thus is recessed in theinsulator and serves as a collar on the insulator 9 to hold the latter immovable end-wise with respect to the shell 2.

Thebase 22 shown in FIGS. 4 and 5 of the drawing,

with the exception of the shape ofthe shell and the inner conical surface 24 of the insulator 25, is similar ,to. that shown in FIGS...1,.2' and 3. Inthisembodiment 4. the shell 23 is a straight sided hollow cylinder having a flat disk end wall 26 provided with an inturned flange 27 of frusto-conical shape the same as flange 8 of FIGS. 1, 2 and 3. The insulator 25 overlaps and covers the ruptured or lacerated edge 28 of the flange 27, as shown at 29, as well as the curved portion 30 of the shell connecting the flange and the flat disk end wall so that in this embodiment also the insulator 25 is formed, in efiect, in its outer surfaceandbetween its ends with a circumferential groove accommodating and engaging the flange 27 and the flange is recessed in the insulator and serves as a collar to hold the insulator immovable with respect to the shell. In molding the plastic glass to form the insulator 25 the glass is forced into the crevices at the splits in the lacerated edge 28. The eyelet contact 31 on the insulator 25 is of conventional structure.

The base shown in FIGS. 4 and 5 is a bayonet type base of commercial structure having extruded pins 32 extending outwardly in diametrically opposite directions for engagement with suitable slots in a well-known type of lamp socket.

The insulator 9 of the base shown in FIGS. 1 to 3 is formed by a procedure similar to that now in use in making commercial bases. As shown in FIG. 6, a mold 33 and a vertically reciprocable die plunger 34 having an integral skirt 35 are used for shaping the insulator. In making the base 1 the shell 2 and the eyelet 10 are inserted in the upwardly opening cavity of the mold 33 which is arranged to hold the shell and the eyelet in proper relation to each other during molding of the insulator. After insertion of the shell and the eyelet a charge of molten glass is dropped into the mold through the flange 8 of the shell 2 and settles down in the bottom of the mold 33. The plunger 34 is then moved from a raised position to a lowered position with respect to the mold in which latter position the annular skirt 35 on the plunger '34 is located around the flange 8, as shown in FIG. 6. The inner diameter of the skirt 35 is only slightly larger than the outer diameter of the edge 18 of the flange 8 so that the skirt closely surrounds said edge asrshown in FIG. 6. The skirt 35 and the pointed end 36 of the plunger 34 are so constructed and arranged that the plastic glass is molded between the mold 33, the flange 8, the end 36 and the skirt 35 which confine the plastic glass as the plunger 34 is moved downward to shape the glass in the form of the insulator shown in FIG. 6.

The part of the plunger above the edge 18 does not engage the said edge at the bottom of the downstroke of the plunger but is spaced therefrom to shape the portion '17 as shown in FIG. 6. During the shaping operation by the plunger the plastic glassis forced into the crevices 19 and over the edge 18 of the flange 8 to partially embed the edge in the glass, to cover the said edge completely, as shown in FIGS. 1 to 3 and 6, and to lock the insulator and'the shell against relative rotation. The portion 17 of the insulator ,9 is thus formed into the shape shown in FIG. 3, in which the outer surface 37 of the portion 17 is cylindrical, to pr ovide, a covering ofsubstantial depth and thickness over the. edge 18 to insure insulation thereof from the inlead wire 12. Good results are obtained when the depth of the glass covering the edge 18 is at least about twice the wall thickness of the shell which in the case of a brass shell is usually in the range of end provided witha conical working face for forming the surface 24 is utilized for shaping. the insulator 25 of the While two species of the invention have been shown and described it will be understood, of course, that changes may be made within the scope of the appended claims without departing from the invention, for example, the re-entrant flange in both species of bases obviously may be in the form of a straight-sided hollow cylinder. However, the frusto-conical shape of the re-entrant flange is preferred because of the greater assurance provided against end-wise movement in an outward direction of the insulator with respect to the shell. While the invention has been shown and described in conjunction with a molded insulator made of glass it will be understood, of course, that an organic thermo-setting plastic material may be used in place of the glass for making the molded insulator and that the base shell may be made of aluminum.

What we claim as new and desire to secure by Letters Patent of the United States is:

l. A lamp base comprising a metal shell contact, a metal perforated center contact, and an insulator molded in the shell and uniting said shell and said center contact and defining a funnel-shaped passage leading into the opening in the center contact from the interior of the shell, said shell having at one end a re-entrant straightsided flange of shorter axial length than that of the insulator, said flange encircling the insulator and said insulator having in its outer surface and between its ends a circumferential groove accommodating and engaging the flange, said insulator extending inward of the shell beyond the terminating edge of said flange and overlapping the said edge, said insulator also extending outward beyond the flanged end of said shell and overlapping the shell at said end whereby the flange serves as a collar on the insulator and the insulator protects the flange from short-circuiting contacts by an inlead wire extending through the base and attached to said center contact.

2. A lamp base comprising a metal shell contact, a metal perforated center contact, and an insulator molded in the shell and uniting said shell and said center contact and defining a funnel-shaped passage leading into the opening in the center contact from the interior of the shell, the shell having at one end a re-entrant straight-sided flange of shorter axial length than that of the insulator and terminating in a lacerated edge within the shell, said flange encircling the insulator and said insulator having in its outer surface and between its ends a circumferential groove accommodating and engaging the flange, said insulator extending inward of the shell beyond the lacerated edge of the flange and overlapping the said edge with the material thereof extending into crevices in the lacerated edge, said insulator also extending outward beyond the flanged end of the shell and overlapping the shell at said end whereby the flange serves as a collar on the insulator and the insulator protects the flange against short-circuiting contacts by an inlead wire extending through the base and attached to said center contact.

3. A lamp base comprising a metal shell contact, a metal perforated center contact, and an insulator molded in the shell and uniting said shell and said center contact and defining a funnel-shaped passage leading into the opening in the center contact from the interior of the shell, the shell having at one end a re-entrant straight-sided flange of frusto-conical shape tapering in the direction of the central axis of the shell toward the said end of the shell, the said flange being of shorter axial length than that of the insulator and terminating in a lacerated edge within the shell, said flange encircling the insulator and said insulator having in its outer surface and between its ends a circumferential groove accommodating and engaging the flange, said insulator extending inward of the shell beyond the lacerated edge of the flange and overlapping the said edge with the material thereof extending into crevices in the lacerated edge, said insulator also extend ing outward beyond the flanged end of the shell and overlapping the shell at said end whereby the flange serves as a collar on the insulator and the insulator protects the flange against short-circuiting contacts by an inlead wire extending through the base and attached to said center contact.

4. A lamp base comprising a metal shell contact, a metal perforated center contact and an insulator molded in the shell and uniting said shell and said center contact and defining a funnel-shaped passage leading into the opening in the center contact from the interior of the shell, said shell having at one end a re-entrant flange of shorter axial length than that of the insulator, said flange encircling the insulator and said insulator having in its outer surface and between its ends a circumferential groove accommodating and engaging the flange, said insulator overlapping the flange at both ends.

References Cited in the file of this patent UNITED STATES PATENTS 537,498 Thompson Apr. 16, 1895 760,065 Gilmore May 17, 1904 775,689 Swan Nov. 22, 1904 905,478 Swan Dec. 1, 1908 1,955,629 Ghysen Apr. 17, 1934 1,965,231 Gustin July 3, 1934 2,403,137 Strickland July 2, 1946 2,519,328 Whitmore et al. Aug. 15, 1950 

